What Is a Boring Head for Mill?

Posted on Dec 24, 2020

Boring Head for Mill

The digital boring head enables quick and easy diameter setting. Some models even include wireless communication. In fact, some are motorized and you can command them to a particular size either using a g-code command (typically to operate the "U" axis) or a handheld remote.

There are no gazebos or boring bars o a typical boring head for a milling machine. The boring bars are real cutters mounted on a boring head. The silver part moves back and forth along the dovetail to change the cutting distance of the rod from the center. This is how you set the page. You can see the knob to adjust this size by turning the tiny screw. Finally, three Allen screws below the larger boring bar locking screws are used to lock the dovetail joint, holding it firmly while cutting.

Why Use Boring Head?

In CNC, we are used to drilling, reaming, or interpolating holes. So when does the boring head appear? The answer is that you usually use a boring bar for larger holes when the tolerances are tight. There is a limit to the accuracy of a hole made by interpolation with an end mill. The problem is backlash and various other positioning errors. We have an article on how to minimize interpolation errors so you will rarely need a boring machine but if the tolerances are tight enough you will need one:

Another reason for using a boring machine is to improve the surface finish of the wall. A typical example of an application that may require a boring head due to tight tolerances would be the machining of a bearing pocket.
 

:: Read More: An Introduction to Boring Machines

CNC Boring and Boring Head Service

There is little trial and error in adjusting the depth of cut to the tolerance of the hole. This makes the use of boring bars quite expensive, so make sure you do interpolation accuracy is set as much as possible to minimize the need for a boring bar. Of course, where there is a need or a problem, there will be alternatives.
 

Boring Boredom Is Not Just Holes

The boring head can also be used for precision outer (outer diameter) turning on a hub with the same ease as it is used for inner (inner) diameter holes. The tip of the cutter point inward to machine the hub. You may also need to switch the direction of rotation to match the expected belt performance. In the video, he rotates the spindle counterclockwise. With digital calipers and micrometers, why not create a digital boring machine? Big Kaiser and many other companies do it!

A digital boring head enables quick and easy diameter setting. Some models even include wireless communication. In fact, some are motorized and you can command them to a particular size either using a g-code command (typically to operate the "U" axis) or a handheld remote.
 

Boring Heads with Automatic Balancing

While counterweights can be attached to balance the boring head for higher revs (see Boring Bar Tips, below), more sophisticated boring heads have an auto-balance feature.

Long ago, in a galaxy far, far away, when manual machining was dominant, automatic boring heads were the kings of a boring world. These heads contained mechanisms that slightly extended the knife with each rotation. The more sophisticated ones could even create tapered holes. Brands like Wohlhaupter and Tree have been associated with these intricate mechanical marvels. Such devices still exist, but we rarely need them for CNC work. It is too easy to interpolate a hole to thicken it and then use a basic boring machine to clean it with an end pass.
 

Boring Bars and Attachments

Many companies make such tools as a replacement for boring bars. Their purpose is to increase stiffness.
 

Boring Feeds and Speeds

Boring channels and speeds are really the same as turning feeds and speeds. The milling cutter does not know whether it is on a lathe as an external turning tool, an ID boring bar, or on a milling machine in external diameter or external diameter boring head-turning.
 

Boring Head Tips

Balance your boring head for higher spins and productivity. Conventional boring heads are quite unbalanced beasts that spin at high revs. The criterion is to limit them to 1000-1500 rpm. But on the other hand, there are other designs that can run faster, so how can G-Wizard know the limits of your particular boring head? We finally agreed that this is something the mechanic needs to consider based on the specific head they have on hand.
 

Vibration Cutting for Precision Boring

I just came across what looks like a great blog from Criterion, boring people. They had a great tip to reduce vibration during machining: make sure the depth of cut is greater than the radius of the cutter. This makes sense and should also apply when turning. Here's how they explain it.

Consider cutting forces when the insert cuts less than the radius. See how the forces are largely trying to push the insert out of the incision. With a deeper cut, more arrows work to stabilize the forces, so not all try to get the liner to lean back and skip the cut. The result is a better finish and less chatter. The need to increase the depth of cut in this situation is just one of the many counterintuitive situations we encounter when machining!

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